Microdialysis is a means of sampling substances from the body to help clinicians assess well-being or metabolic conditions by providing serial biochemical samples from a catheter which lies within the substance of an organ. Current commercial microdialysis systems are equipped for sample collection, handling, and analysis of small molecules including glucose, lactate, pyruvate and glycerol as markers of cell injury. Sample collection is based on passive diffusion through a semi-permeable membrane placed at the end of a catheter.
Microdialysis sampling can be performed on organs which move. For example microdialysis sampling can be used to study metabolic aspects of the beating heart. When a microdialysis probe is placed into the substance of a beating heart, there is always concern that the catheter position can be disturbed by the heart's contractions as well as risk for damage to heart tissue as well as the catheter when inserting the microdialysis probe. These risks are taken because it has been shown that the microdialysis technique gives a more rapid response compared to ECG monitoring, catecholamine analyses or other clinical signs of cardiac ischemia.
When a microdialysis catheter is placed in a tissue or organ, there will unavoidably be some tissue damage. If the microdialysis method is used clinically to monitor for example a myocardial metabolic state, it is important to minimize the damage associated with probe insertion. The tissue damage caused by probe placement makes it necessary to allow an equilibration period of 60 to 90 minutes before reliable data can be obtained and this is done in order to allow local resorption or redistribution of fluid that may have initially accumulated surrounding the catheter at the time of insertion. If the time needed for this equilibration period could be shortened or eliminated altogether, this would allow for a more efficacious clinical application of microdialysis sampling.
There is a clear need for a device and method that can sample changes in interstitial fluid concentrations of small molecules which agree strongly with microdialysis sampling direct from the interstitium which alleviates the above mentioned problems associated with microdialysis sampling from a probe placed in the substance of an organ, for example the heart wall.